Python & CircuitPython

It's easy to use the ADS1115 and ADS1015 ADC with CircuitPython and the Adafruit CircuitPython ADS1x15 module.  This module allows you to easily write Python code that reads the analog input values.

You can use this ADC with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.

CircuitPython Microcontroller Wiring

First wire up the ADC to your board exactly as shown on the previous pages for Arduino using an I2C interface.  Here's an example of wiring a Feather M0 to the ADS1115 with I2C:

  • Board 3V to ADS1115 VDD - Remember the maximum input voltage to any ADC channel cannot exceed this VDD 3V value!
  • Board GND to ADS1115 GND
  • Board SCL to ADS1115 SCL
  • Board SDA to ADS1115 SDA

Python Computer Wiring

Since there's dozens of Linux computers/boards you can use we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported

Here's the Raspberry Pi wired to the ADS1015 with I2C:

  • Pi 3V to ADS1015 VDD - Remember the maximum input voltage to any ADC channel cannot exceed this VDD 3V value!
  • Pi GND to ADS1015 GND
  • Pi SCL to ADS1015 SCL
  • Pi SDA to ADS1015 SDA

CircuitPython Installation of ADS1x15Library

Next you'll need to install the Adafruit CircuitPython ADS1x15 library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  For example the Circuit Playground Express guide has a great page on how to install the library bundle for both express and non-express boards.

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/Metro M0 basic you'll need to manually install the necessary libraries from the bundle:

  • adafruit_ads1x15
  • adafruit_bus_device

You can also download the adafruit_ads1x15 folder from its releases page on Github.

Before continuing make sure your board's lib folder or root filesystem has the adafruit_ads1x15 and adafruit_bus_device files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

Python Installation of ADS1x15 Library

You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!

Once that's done, from your command line run the following command:

  • sudo pip3 install adafruit-circuitpython-ads1x15

If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

CircuitPython & Python Usage

To demonstrate the usage of the ADC we will initialize it and read the ADC channel values interactively using the REPL.  First run the following code to import the necessary modules and initialize the I2C bus:

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import board
import busio
i2c = busio.I2C(board.SCL, board.SDA)

Next, import the module for the board you are using. For the ADS1015, use:

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import adafruit_ads1x15.ads1015 as ADS

OR, for the ADS1115, use:

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import adafruit_ads1x15.ads1115 as ADS

Note that we are renaming each import to ADS for convenience.

The final import needed is for the ADS1x15 library's version of AnalogIn:

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from adafruit_ads1x15.analog_in import AnalogIn

which provides behavior similar to the core AnalogIn library, but is specific to the ADS1x15 ADC's.

OK, now we can actually create the ADC object. For the ADS1015, use:

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ads = ADS.ADS1015(i2c)

OR, for the ADS1115, use:

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ads = ADS.ADS1115(i2c)

Now let's see how to get values from the board. You can use these boards in either single ended or differential mode. The usage for the two modes are slightly different, so we'll go over them separately.

Single Ended Mode

For single ended mode we use AnalogIn to create the analog input channel, providing the ADC object and the pin to which the signal is attached. Here, we use pin 0:

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chan = AnalogIn(ads, ADS.P0)

To set up additional channels, use the same syntax but provide a different pin.

Now you can read the raw value and voltage of the channel using either the the value or voltage property.

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print(chan.value, chan.voltage)

Differential Mode

For differential mode, you provide two pins when setting up the ADC channel. The reading will be the difference between the two. Here, we use pin 0 and 1:

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chan = AnalogIn(ads, ADS.P0, ADS.P1)

You can create more channels by doing this again with different pins. However, note that not all pin combinations are possible. See the datasheets for details.

Once the channel is created, getting the readings is the same as before:

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print(chan.value, chan.voltage)

Gain

Both the ADS1015 and the ADS1115 have a Programmable Gain (PGA) that you can set to amplify the incoming signal before it reaches the ADC. The available settings and associated Full Scale (FS) voltage range are shown in Table 3 of the datasheet.

You set the gain to one of the values using the gain property, like this:

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ads.gain = 16

Note that setting gain will affect the raw ADC value but not the voltage (expect for variance due to noise). For example:

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>>> ads.gain
1
>>> chan.value, chan.voltage
(84, 0.168082)
>>> ads.gain = 16
>>> ads.gain
16
>>> chan.value, chan.voltage
(1335, 0.167081)
>>> 

The value changed from 84 to 1335, which is pretty close to 84 x 16 = 1344. However, the voltage returned in both cases is still the actual input voltage of ~0.168 V.

More Info

The above examples cover the basic setup and usage using default settings. For more details, see the documentation.

This guide was first published on Nov 29, 2012. It was last updated on Nov 29, 2012. This page (Python & CircuitPython) was last updated on Aug 22, 2019.